In jet-propelled missiles, such as spin-stabilized spherical missiles, a solid propellent motor chamber forms a combustion chamber for the missile. The chamber is filled or nearly filled with a solid propellent material either combined with or in conjunction with an igniter substance. Upon ignition, the solid propellent burns very rapidly to produce considerable volumes of gas that is exhausted at high velocity through a restricted nozzle, thereby producing thrust for the missile. The size of the nozzle is relatively small in comparison to the size of the combustion chamber. With the volume of generated gas from combustion being quite large, high pressures often are built up in the combustion chamber which can approach the bursting strength of the propellent/motor casing These are very dangerous conditions and can cause a catastrophe, particularly in environments of spherical spin-stabilized missiles which are mounted on the ends of rifles operated in close proximity by an individual. The term "spherical" herein is being used in a generic sense to mean line-of-sight projectiles or missiles.
Consequently, it would be highly desirable to provide safety measures to prevent premature bursting of such missiles as a result of excessive pressure built up within the combustion chamber by rapidly relieving the pressure whenever the pressure becomes dangerously high.
Heretofore, various pressure responsive safety devices have been proposed for jet-propulsion motors, such as the devices disclosed in U.S. Pat. Nos. 2,958,184 and 2,958,185 to V. M. Sanders, both dated Nov. 1, 1960. The devices shown in these patents generally include a rupturable diaphragm fitted along with a nozzle in a housing and positioned in such a manner that the diaphragm ruptures to prevent a high pressure from bursting the combustion chamber. The gasses that escape through the ruptured diaphragm are ducted and released to the atmosphere perpendicular to the normal longitudinal axis of the motor.
One of the problems with prior rupturable safety devices, particularly devices of the rupturable diaphragm type described above, is that the ruptured diaphragms tend to cause the expulsion of fragments which, in certain environments, can be as dangerous to personnel as the actual bursting of the missile itself. In addition, particularly with spin-stabilized spherical missiles, transverse expulsion of the exhausted gasses can cause the missiles to break away from their receptacles and become out of control. Still further, the bursting of a diaphragm often is not symmetrical and again, this can be critical with a symmetrical, spherical spin-stabilized jet-propelled missile.
This invention is directed to solving the above problems by providing a novel means for relieving excessive pressure within the combustion chamber of a jet-propelled missile wherein the safety valve means is unitary and is captured bodily within the missile itself, along with symmetrical exhaustion of the excessive gasses.